{"abstract":"X-terminated and many digit-terminated ISBNs are judged incorrectly.","category":"Check-digit algorithms","checks":8,"contract":"ISBN-10 validation. Hyphens and spaces are removed; the rest must be nine ASCII digits followed by a digit or uppercase X (value 10), else \"malformed\". Weights run 10 down to 1 from the left and the number is \"valid\" when the weighted sum is divisible by 11, else \"invalid\".","evaluation_group":"w2-check_digit_algorithms-isbn10-validate","failed_approach":"Folding the mod-11 remainder through % 10 also accepts sums with remainder 10.","family":"w2-check_digit_algorithms-isbn10-validate-modulus","id":"FA-72426","implementations":{"attempt":{"sha256":"9f0a3e530aa7341cea2fd9c2df1692691a3fd92fe9cb96789c4c024be920c2d0","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(s):\n    t = s.replace('-', '').replace(' ', '')\n    if len(t) != 10 or not t.isascii() or not t[:9].isdigit():\n        return 'malformed'\n    if not (t[9].isdigit() or t[9] == 'X'):\n        return 'malformed'\n    total = 0\n    for i, ch in enumerate(t):\n        v = 10 if ch == 'X' else int(ch)\n        total += (10 - i) * v\n    return 'valid' if total % 11 % 10 == 0 else 'invalid'\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nfixtures = [[['regression [\"5892872939\"]', ['5892872939'], 'valid'], ['regression [\"2399553950\"]', ['2399553950'], 'valid'], ['partial-repair [\"5892872938\"]', ['5892872938'], 'invalid'], ['partial-repair [\"9465545448\"]', ['9465545448'], 'invalid'], ['control [\"0000000000\"]', ['0000000000'], 'valid'], ['control [\"123456789X\"]', ['123456789X'], 'valid'], ['control [\"5892872930\"]', ['5892872930'], 'invalid'], ['control [\"2399553951\"]', ['2399553951'], 'invalid']], [['regression [\"829284466X\"]', ['829284466X'], 'valid'], ['regression [\"9379774826\"]', ['9379774826'], 'valid'], ['partial-repair [\"9379774825\"]', ['9379774825'], 'invalid'], ['partial-repair [\"2266685685\"]', ['2266685685'], 'invalid'], ['control [\"8292844660\"]', ['8292844660'], 'invalid'], ['control [\"9379774827\"]', ['9379774827'], 'invalid'], ['control [\"2266685687\"]', ['2266685687'], 'invalid'], ['control [\"2892681791\"]', ['2892681791'], 'invalid']], [['regression [\"2892681790\"]', ['2892681790'], 'valid'], ['regression [\"5900307905\"]', ['5900307905'], 'valid'], ['partial-repair [\"5892872938\"]', ['5892872938'], 'invalid'], ['partial-repair [\"9465545448\"]', ['9465545448'], 'invalid'], ['control [\"99921-58-10-7\"]', ['99921-58-10-7'], 'valid'], ['control [\"03064061\"]', ['03064061'], 'malformed'], ['control [\"030640615X1\"]', ['030640615X1'], 'malformed'], ['control [\"0306406X52\"]', ['0306406X52'], 'malformed']], [['regression [\"7113753523\"]', ['7113753523'], 'valid'], ['regression [\"1475433131\"]', ['1475433131'], 'valid'], ['partial-repair [\"9379774825\"]', ['9379774825'], 'invalid'], ['partial-repair [\"2266685685\"]', ['2266685685'], 'invalid'], ['control [\"0000000000\"]', ['0000000000'], 'valid'], ['control [\"123456789X\"]', ['123456789X'], 'valid'], ['control [\"5892872930\"]', ['5892872930'], 'invalid'], ['control [\"2399553951\"]', ['2399553951'], 'invalid']], [['regression [\"8449627923\"]', ['8449627923'], 'valid'], ['regression [\"0436178273\"]', ['0436178273'], 'valid'], ['partial-repair [\"5892872938\"]', ['5892872938'], 'invalid'], ['partial-repair [\"9465545448\"]', ['9465545448'], 'invalid'], ['control [\"8292844660\"]', ['8292844660'], 'invalid'], ['control [\"9379774827\"]', ['9379774827'], 'invalid'], ['control [\"2266685687\"]', ['2266685687'], 'invalid'], ['control [\"2892681791\"]', ['2892681791'], 'invalid']]]\nfor label, args, expected in fixtures[N - 1]:\n    check(label, solve(*args), expected)\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"},"broken":{"sha256":"cbf1c644354d519bf83b8fbcc863c0d7017e90e1cae7647f836a3beca95e230a","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(s):\n    t = s.replace('-', '').replace(' ', '')\n    if len(t) != 10 or not t.isascii() or not t[:9].isdigit():\n        return 'malformed'\n    if not (t[9].isdigit() or t[9] == 'X'):\n        return 'malformed'\n    total = 0\n    for i, ch in enumerate(t):\n        v = 10 if ch == 'X' else int(ch)\n        total += (10 - i) * v\n    return 'valid' if total % 10 == 0 else 'invalid'\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nfixtures = [[['regression [\"5892872939\"]', ['5892872939'], 'valid'], ['regression [\"2399553950\"]', ['2399553950'], 'valid'], ['partial-repair [\"5892872938\"]', ['5892872938'], 'invalid'], ['partial-repair [\"9465545448\"]', ['9465545448'], 'invalid'], ['control [\"0000000000\"]', ['0000000000'], 'valid'], ['control [\"123456789X\"]', ['123456789X'], 'valid'], ['control [\"5892872930\"]', ['5892872930'], 'invalid'], ['control [\"2399553951\"]', ['2399553951'], 'invalid']], [['regression [\"829284466X\"]', ['829284466X'], 'valid'], ['regression [\"9379774826\"]', ['9379774826'], 'valid'], ['partial-repair [\"9379774825\"]', ['9379774825'], 'invalid'], ['partial-repair [\"2266685685\"]', ['2266685685'], 'invalid'], ['control [\"8292844660\"]', ['8292844660'], 'invalid'], ['control [\"9379774827\"]', ['9379774827'], 'invalid'], ['control [\"2266685687\"]', ['2266685687'], 'invalid'], ['control [\"2892681791\"]', ['2892681791'], 'invalid']], [['regression [\"2892681790\"]', ['2892681790'], 'valid'], ['regression [\"5900307905\"]', ['5900307905'], 'valid'], ['partial-repair [\"5892872938\"]', ['5892872938'], 'invalid'], ['partial-repair [\"9465545448\"]', ['9465545448'], 'invalid'], ['control [\"99921-58-10-7\"]', ['99921-58-10-7'], 'valid'], ['control [\"03064061\"]', ['03064061'], 'malformed'], ['control [\"030640615X1\"]', ['030640615X1'], 'malformed'], ['control [\"0306406X52\"]', ['0306406X52'], 'malformed']], [['regression [\"7113753523\"]', ['7113753523'], 'valid'], ['regression [\"1475433131\"]', ['1475433131'], 'valid'], ['partial-repair [\"9379774825\"]', ['9379774825'], 'invalid'], ['partial-repair [\"2266685685\"]', ['2266685685'], 'invalid'], ['control [\"0000000000\"]', ['0000000000'], 'valid'], ['control [\"123456789X\"]', ['123456789X'], 'valid'], ['control [\"5892872930\"]', ['5892872930'], 'invalid'], ['control [\"2399553951\"]', ['2399553951'], 'invalid']], [['regression [\"8449627923\"]', ['8449627923'], 'valid'], ['regression [\"0436178273\"]', ['0436178273'], 'valid'], ['partial-repair [\"5892872938\"]', ['5892872938'], 'invalid'], ['partial-repair [\"9465545448\"]', ['9465545448'], 'invalid'], ['control [\"8292844660\"]', ['8292844660'], 'invalid'], ['control [\"9379774827\"]', ['9379774827'], 'invalid'], ['control [\"2266685687\"]', ['2266685687'], 'invalid'], ['control [\"2892681791\"]', ['2892681791'], 'invalid']]]\nfor label, args, expected in fixtures[N - 1]:\n    check(label, solve(*args), expected)\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"},"fixed":{"sha256":"5ee45dd275ecc7161ebedd6207c8c41d261febce4b1240e5f4dd969b5878b5bb","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(s):\n    t = s.replace('-', '').replace(' ', '')\n    if len(t) != 10 or not t.isascii() or not t[:9].isdigit():\n        return 'malformed'\n    if not (t[9].isdigit() or t[9] == 'X'):\n        return 'malformed'\n    total = 0\n    for i, ch in enumerate(t):\n        v = 10 if ch == 'X' else int(ch)\n        total += (10 - i) * v\n    return 'valid' if total % 11 == 0 else 'invalid'\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nfixtures = [[['regression [\"5892872939\"]', ['5892872939'], 'valid'], ['regression [\"2399553950\"]', ['2399553950'], 'valid'], ['partial-repair [\"5892872938\"]', ['5892872938'], 'invalid'], ['partial-repair [\"9465545448\"]', ['9465545448'], 'invalid'], ['control [\"0000000000\"]', ['0000000000'], 'valid'], ['control [\"123456789X\"]', ['123456789X'], 'valid'], ['control [\"5892872930\"]', ['5892872930'], 'invalid'], ['control [\"2399553951\"]', ['2399553951'], 'invalid']], [['regression [\"829284466X\"]', ['829284466X'], 'valid'], ['regression [\"9379774826\"]', ['9379774826'], 'valid'], ['partial-repair [\"9379774825\"]', ['9379774825'], 'invalid'], ['partial-repair [\"2266685685\"]', ['2266685685'], 'invalid'], ['control [\"8292844660\"]', ['8292844660'], 'invalid'], ['control [\"9379774827\"]', ['9379774827'], 'invalid'], ['control [\"2266685687\"]', ['2266685687'], 'invalid'], ['control [\"2892681791\"]', ['2892681791'], 'invalid']], [['regression [\"2892681790\"]', ['2892681790'], 'valid'], ['regression [\"5900307905\"]', ['5900307905'], 'valid'], ['partial-repair [\"5892872938\"]', ['5892872938'], 'invalid'], ['partial-repair [\"9465545448\"]', ['9465545448'], 'invalid'], ['control [\"99921-58-10-7\"]', ['99921-58-10-7'], 'valid'], ['control [\"03064061\"]', ['03064061'], 'malformed'], ['control [\"030640615X1\"]', ['030640615X1'], 'malformed'], ['control [\"0306406X52\"]', ['0306406X52'], 'malformed']], [['regression [\"7113753523\"]', ['7113753523'], 'valid'], ['regression [\"1475433131\"]', ['1475433131'], 'valid'], ['partial-repair [\"9379774825\"]', ['9379774825'], 'invalid'], ['partial-repair [\"2266685685\"]', ['2266685685'], 'invalid'], ['control [\"0000000000\"]', ['0000000000'], 'valid'], ['control [\"123456789X\"]', ['123456789X'], 'valid'], ['control [\"5892872930\"]', ['5892872930'], 'invalid'], ['control [\"2399553951\"]', ['2399553951'], 'invalid']], [['regression [\"8449627923\"]', ['8449627923'], 'valid'], ['regression [\"0436178273\"]', ['0436178273'], 'valid'], ['partial-repair [\"5892872938\"]', ['5892872938'], 'invalid'], ['partial-repair [\"9465545448\"]', ['9465545448'], 'invalid'], ['control [\"8292844660\"]', ['8292844660'], 'invalid'], ['control [\"9379774827\"]', ['9379774827'], 'invalid'], ['control [\"2266685687\"]', ['2266685687'], 'invalid'], ['control [\"2892681791\"]', ['2892681791'], 'invalid']]]\nfor label, args, expected in fixtures[N - 1]:\n    check(label, solve(*args), expected)\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"}},"limitations":"A deterministic, bounded teaching model of the named scheme under the stated contract; not a certified validator. This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.","method":"Deterministic executable model with adversarial boundary fixtures.","provenance":{"created_by":"Failure Map","dependencies":"Python standard library","family":"w2-check_digit_algorithms-isbn10-validate-modulus","generated_at":"2026-09-29T14:48:38.429524+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"Catalogue and bookstore systems validate legacy ISBN-10 identifiers on intake.","repair":"ISBN-10 is a mod-11 scheme; test total % 11 == 0.","root_cause":"The weighted sum is tested with % 10 instead of % 11.","sha256":"360919c1f7440aa9f69032d296a80862dbb62b353e1d7a9312917c0ab87cdf8f","title":"ISBN-10 validates the weighted sum modulo ten · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":37.426,"exit_code":1,"observations":[{"actual":"valid","check":"regression [\"5892872939\"]","expected":"valid","passed":true},{"actual":"valid","check":"regression [\"2399553950\"]","expected":"valid","passed":true},{"actual":"valid","check":"partial-repair [\"5892872938\"]","expected":"invalid","passed":false},{"actual":"valid","check":"partial-repair [\"9465545448\"]","expected":"invalid","passed":false},{"actual":"valid","check":"control [\"0000000000\"]","expected":"valid","passed":true},{"actual":"valid","check":"control [\"123456789X\"]","expected":"valid","passed":true},{"actual":"invalid","check":"control [\"5892872930\"]","expected":"invalid","passed":true},{"actual":"invalid","check":"control [\"2399553951\"]","expected":"invalid","passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"regression [\\\"5892872939\\\"]\", \"actual\": \"valid\", \"expected\": \"valid\", \"passed\": true}, {\"check\": \"regression [\\\"2399553950\\\"]\", \"actual\": \"valid\", \"expected\": \"valid\", \"passed\": true}, {\"check\": \"partial-repair [\\\"5892872938\\\"]\", \"actual\": \"valid\", \"expected\": \"invalid\", \"passed\": false}, {\"check\": \"partial-repair [\\\"9465545448\\\"]\", \"actual\": \"valid\", \"expected\": \"invalid\", \"passed\": false}, {\"check\": \"control [\\\"0000000000\\\"]\", \"actual\": \"valid\", \"expected\": \"valid\", \"passed\": true}, {\"check\": \"control [\\\"123456789X\\\"]\", \"actual\": \"valid\", \"expected\": \"valid\", \"passed\": true}, {\"check\": \"control [\\\"5892872930\\\"]\", \"actual\": \"invalid\", \"expected\": \"invalid\", \"passed\": true}, {\"check\": \"control [\\\"2399553951\\\"]\", \"actual\": \"invalid\", \"expected\": \"invalid\", \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":39.188,"exit_code":1,"observations":[{"actual":"invalid","check":"regression [\"5892872939\"]","expected":"valid","passed":false},{"actual":"invalid","check":"regression [\"2399553950\"]","expected":"valid","passed":false},{"actual":"valid","check":"partial-repair [\"5892872938\"]","expected":"invalid","passed":false},{"actual":"invalid","check":"partial-repair [\"9465545448\"]","expected":"invalid","passed":true},{"actual":"valid","check":"control [\"0000000000\"]","expected":"valid","passed":true},{"actual":"valid","check":"control [\"123456789X\"]","expected":"valid","passed":true},{"actual":"invalid","check":"control [\"5892872930\"]","expected":"invalid","passed":true},{"actual":"invalid","check":"control [\"2399553951\"]","expected":"invalid","passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"regression [\\\"5892872939\\\"]\", \"actual\": \"invalid\", \"expected\": \"valid\", \"passed\": false}, {\"check\": \"regression [\\\"2399553950\\\"]\", \"actual\": \"invalid\", \"expected\": \"valid\", \"passed\": false}, {\"check\": \"partial-repair [\\\"5892872938\\\"]\", \"actual\": \"valid\", \"expected\": \"invalid\", \"passed\": false}, {\"check\": \"partial-repair [\\\"9465545448\\\"]\", \"actual\": \"invalid\", \"expected\": \"invalid\", \"passed\": true}, {\"check\": \"control [\\\"0000000000\\\"]\", \"actual\": \"valid\", \"expected\": \"valid\", \"passed\": true}, {\"check\": \"control [\\\"123456789X\\\"]\", \"actual\": \"valid\", \"expected\": \"valid\", \"passed\": true}, {\"check\": \"control [\\\"5892872930\\\"]\", \"actual\": \"invalid\", \"expected\": \"invalid\", \"passed\": true}, {\"check\": \"control [\\\"2399553951\\\"]\", \"actual\": \"invalid\", \"expected\": \"invalid\", \"passed\": true}], \"passed\": false}\n"},"fixed":{"elapsed_ms":38.331,"exit_code":0,"observations":[{"actual":"valid","check":"regression [\"5892872939\"]","expected":"valid","passed":true},{"actual":"valid","check":"regression [\"2399553950\"]","expected":"valid","passed":true},{"actual":"invalid","check":"partial-repair [\"5892872938\"]","expected":"invalid","passed":true},{"actual":"invalid","check":"partial-repair [\"9465545448\"]","expected":"invalid","passed":true},{"actual":"valid","check":"control [\"0000000000\"]","expected":"valid","passed":true},{"actual":"valid","check":"control [\"123456789X\"]","expected":"valid","passed":true},{"actual":"invalid","check":"control [\"5892872930\"]","expected":"invalid","passed":true},{"actual":"invalid","check":"control [\"2399553951\"]","expected":"invalid","passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"regression [\\\"5892872939\\\"]\", \"actual\": \"valid\", \"expected\": \"valid\", \"passed\": true}, {\"check\": \"regression [\\\"2399553950\\\"]\", \"actual\": \"valid\", \"expected\": \"valid\", \"passed\": true}, {\"check\": \"partial-repair [\\\"5892872938\\\"]\", \"actual\": \"invalid\", \"expected\": \"invalid\", \"passed\": true}, {\"check\": \"partial-repair [\\\"9465545448\\\"]\", \"actual\": \"invalid\", \"expected\": \"invalid\", \"passed\": true}, {\"check\": \"control [\\\"0000000000\\\"]\", \"actual\": \"valid\", \"expected\": \"valid\", \"passed\": true}, {\"check\": \"control [\\\"123456789X\\\"]\", \"actual\": \"valid\", \"expected\": \"valid\", \"passed\": true}, {\"check\": \"control [\\\"5892872930\\\"]\", \"actual\": \"invalid\", \"expected\": \"invalid\", \"passed\": true}, {\"check\": \"control [\\\"2399553951\\\"]\", \"actual\": \"invalid\", \"expected\": \"invalid\", \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}